Now imagine a tribe of people, an ethnicity that is genetically adapted to survive underwater without oxygen for at least 13 minutes on an average. The Bajau Laut people of Southeast Asia are not specially trained in modern static apnea, but they’ve been discovered to have evolved physiologically and genetically, gaining new features that have basically turned them to human seals .
The diving reflex is a group of automatic responses that occur when the face of an air-breathing mammal is submerged into water. Your blood vessels constrict, your spleen contracts, and your heart rate slows in response to being low on oxygen. Your body will try to maximize its oxygen reserves until you can breathe in oxygen again. The splenic contraction is especially important as it releases red blood cells and increases the oxygen capacity of the blood.
The Bajau people are a seafaring, nomadic, fishing clan who spend almost 60 percent of their life deep-diving underwater. A 2018 study published in the Journal Cell found that they may have evolved to have larger spleens, estimably 50 percent bigger than that of an average person . This enables them to maintain the diving reflex for much longer while underwater. An enlarged spleen would mean a more sufficient red blood cell reservoir for deep-diving purposes. More red blood cells would mean that you would be able to carry more oxygen in your blood, allowing for longer dives. Essentially improving how efficient we are at utilizing the oxygen we breathe in.
The Bajau are subsistent people found in the waters off Indonesia, Malaysia, and the Philippines, living in long houseboats known as lepas. They fish for their food and only come to the town to trade for other items or to seek shelter from storms. The Bajau have lived on the sea for many centuries and about 200 years ago, some populations began to settle on the shores, especially in and on the coasts of Malaysia .
They have several traditional methods of fishing, with diving being the most common. Using wooden goggles and hand weights, they swim as deep as 30 meters (100 feet) into the water to catch fish for survival. They also love to dive for a particular sea cucumber species known as trepang, with which local delicacies and soups are mad
The researchers found that members of the tribe who do not dive also have the genetic mutation of an enlarged spleen. They suspect that a particular gene known as PDE10A might be responsible for the mutation in the Bajau. PDE10A controls a thyroid hormone known as T4 which increases metabolic rates and combats low oxygen levels in times of distress. T4 has been linked to larger spleen sizes in mice. Also, mice that have been manipulated to have lower amounts of T4 would end up with smaller spleens.
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